Kavli Affiliate: Kiyoshi W. Masui
| First 5 Authors: Danté M. Hewitt, Mohit Bhardwaj, Alexa C. Gordon, Aida Kirichenko, Kenzie Nimmo
| Summary:
We present the localization and host galaxy of FRB 20190208A, a repeating
source of fast radio bursts (FRBs) discovered using CHIME/FRB. As part of the
PRECISE repeater localization program on the EVN, we monitored FRB 20190208A
for 65.6 hours at $sim1.4$ GHz and detected a single burst, which led to its
VLBI localization with 260 mas uncertainty (2$sigma$). Follow-up optical
observations with the MMT Observatory ($igtrsim 25.7$ mag (AB)) found no
visible host at the FRB position. Subsequent deeper observations with the GTC,
however, revealed an extremely faint galaxy ($r=27.32 pm0.16$ mag), very
likely ($99.95 %$) associated with FRB 20190208A. Given the dispersion measure
of the FRB ($sim580$ pc cm$^{-3}$), even the most conservative redshift
estimate ($z_{mathrm{max}}sim0.83$) implies that this is the
lowest-luminosity FRB host to date ($lesssim10^8L_{odot}$), even less
luminous than the dwarf host of FRB 20121102A. We investigate how localization
precision and the depth of optical imaging affect host association, and discuss
the implications of such a low-luminosity dwarf galaxy. Unlike the other
repeaters with low-luminosity hosts, FRB 20190208A has a modest Faraday
rotation measure of a few tens of rad m$^{-2}$, and EVN plus VLA observations
reveal no associated compact persistent radio source. We also monitored FRB
20190208A for 40.4 hours over 2 years as part of the ‘ECLAT repeating FRB
monitoring campaign on the Nanc{c}ay Radio Telescope, and detected one burst.
Our results demonstrate that, in some cases, the robust association of an FRB
with a host galaxy will require both high localization precision, as well as
deep optical follow-up.
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